Reflections on tissue characterisation.

Theoretical predictions that absorption and velocity dispersion, in addition to characteristic acoustic impedance mismatch, mediate the reflectivity of a planar interface are explored. A technique to measure the frequency dependence of the reflectivity is described: a special hydrophone, purpose-built to this end, is utilised in order to show that perspex/water and neoprene/water reflectivities are not inconsistent with the general predictions of the theory. An approach towards displaying, simultaneously, both the temporal and spectral properties of ultrasound pulses is described, and its potential utility in both reflectivity measurement and investigation of non-linear propagation is proposed.